Multilayer ceramic capacitor and method of manufacturing the same

ABSTRACT

A multilayer ceramic capacitor includes a multilayer body including a plurality of stacked dielectric layers including a dielectric ceramic that includes a plurality of crystal grains and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric layers, and external electrodes. The multilayer body includes a Ba and Ti containing perovskite compound, La, Mg, Mn and Al, and satisfies conditions such that in a case in which a content of Ti is set to 100 molar parts, a fraction of each content of La, Mg, Mn and Al relative to the content of Ti is such that La is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molar part or less, Mn is about 1.0 to about 3.0 molar parts and Al is about 0.5 to about 2.5 molar parts, and an average number of crystal grains included in each of the dielectric layers in the stacking direction is one or more to three or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayer ceramic capacitor and amethod for manufacturing the same, and in particular relates to amultilayer ceramic capacitor including a multilayer body provided with aplurality of stacked dielectric layers and a plurality of internalelectrodes disposed at a plurality of interfaces between the dielectriclayers, and an external electrode provided on an outer surface of themultilayer body and electrically connected to some of the innerelectrodes and a method for manufacturing the same.

2. Description of the Related Art

In recent years, a multilayer ceramic capacitor which is compact in sizebut can offer a large capacitance has been widely used in an electronicdevice to make the electronic device small in size and light in weight.For example, as illustrated in FIG. 2, the multilayer ceramic capacitoris configured to include a multilayer body 10 provided with a pluralityof stacked dielectric layers (dielectric ceramic layers) 11 and aplurality of internal electrodes 12 disposed at a plurality ofinterfaces between dielectric layers 11, and a pair of externalelectrodes 13 a and 13 b disposed on both end surfaces of multilayerbody 10 in conduction with internal electrodes 12 exposed alternately onopposite end surfaces.

In the multilayer ceramic capacitor mentioned above, as a material forforming the dielectric layers, a dielectric ceramic material which has ahigh relative dielectric constant and includes a Ba and Ti containingperovskite compound as a primary ingredient has been widely used.

As the dielectric ceramic material, a non-reducible dielectric ceramiccomposition is proposed (see Japanese Patent Laying-Open No. 4-169003).The non-reducible dielectric ceramic composition contains BaTiO₃ at 95.0to 98.0 mol % and rare earth oxide at 2.0 to 5.0 mol % as a principalcomponent, and contains MnO and oxide glass mainly composed ofBaO—SrO—Li₂O—SiO₂ as a minor component. In BaTiO₃, the content ofunreacted BaO is 0.7 wt % or less and a ratio of Ba/Ti is 1.005 to1.025. The rare earth oxide contains at least one element selected fromLa, Nd, Sm, Dy and Er. If the principal component is set to 100 parts byweight, MnO is 0.3 to 1.5 parts by weight and the oxide glass is 0.5 to2.5 parts by weight.

Since the non-reducible dielectric ceramic composition is superior incapacitance-temperature characteristics, when it is used as a dielectriclayer (dielectric ceramic layer) in a multilayer ceramic capacitor, itis possible to make the dielectric layer thinner.

However, based on the material composition of the non-reducibledielectric ceramic composition of the prior art, when it is used as anextremely thinned dielectric layer in a multilayer ceramic capacitor,the aging variation in insulation resistance in a high temperature loadtest will be great, which makes it impossible to obtain a multilayerceramic capacitor with sufficient reliability.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a multilayerceramic capacitor having a small aging variation in insulationresistance in a high temperature load test, a superior insulationdeterioration tolerance and a high reliability, and a method formanufacturing the same.

A multilayer ceramic capacitor according to a preferred embodiment ofthe present invention includes a multilayer body provided with aplurality of stacked dielectric layers including a dielectric ceramicthat includes a plurality of crystal grains and a plurality of internalelectrodes disposed at a plurality of interfaces between the dielectriclayers, and an external electrode provided on an outer surface of themultilayer body and electrically connected to some of the plurality ofinner electrodes. The multilayer body includes a Ba and Ti containingperovskite compound and La, Mg, Mn and Al. In a case in which a contentof Ti is set to 100 molar parts, a fraction of each content of La, Mg,Mn and Al relative to the content of Ti is such that La is about 0.2 toabout 1.2 molar parts, Mg is about 0.1 molar part or less, Mn is about1.0 to about 3.0 molar parts and Al is about 0.5 to about 2.5 molarparts, and an average number of crystal grains included in each of thedielectric layers in the stacking direction is one or more to three orless.

Further, a multilayer ceramic capacitor according to another preferredembodiment of the present invention includes a multilayer body providedwith a plurality of stacked dielectric layers including a dielectricceramic that includes a plurality of crystal grains and a plurality ofinternal electrodes disposed at a plurality of interfaces between thedielectric layers, and an external electrode provided on an outersurface of the multilayer body and electrically connected to some of theplurality of inner electrodes. The multilayer body includes a Ba and Ticontaining perovskite compound and La, Mg, Mn and Al. In a case in whichthe multilayer body is subjected to a dissolution treatment to form asolution and a content of Ti is set to 100 molar parts, a fraction ofeach content of La, Mg, Mn and Al relative to the content of Ti is suchthat La is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molarpart or less, Mn is about 1.0 to about 3.0 molar parts and Al is about0.5 to about 2.5 molar parts, and an average number of crystal grainsincluded in each of the dielectric layers in the stacking direction isone or more to three or less.

In the present invention, “the multilayer body being subjected to adissolution treatment to form a solution” conceptually means that themultilayer body is made to form a solution by dissolving it in acid, orthe multilayer body is made to form a solution by subjecting it toalkali fusion and then dissolving it in acid or by any other ways, andthus, no particular restriction is applied to the method for forming asolution by the dissolution treatment.

Furthermore, a multilayer ceramic capacitor according to a furtherpreferred embodiment of the present invention includes a multilayer bodyprovided with a plurality of stacked dielectric layers including adielectric ceramic that includes a plurality of crystal grains and aplurality of internal electrodes disposed at a plurality of interfacesbetween the dielectric layers, and an external electrode provided on anouter surface of the multilayer body and electrically connected to someof the plurality of inner electrodes. Each of the plurality ofdielectric layers includes a Ba and Ti containing perovskite compoundand La, Mg, Mn and Al. In a case in which a content of Ti is set to 100molar parts, a fraction of each content of La, Mg, Mn and Al relative tothe content of Ti is such that La is about 0.2 to about 1.2 molar parts,Mg is about 0.1 molar part or less, Mn is about 1.0 to about 3.0 molarparts and Al is about 0.5 to about 2.5 molar parts, and an averagenumber of crystal grains included in each of the dielectric layers inthe stacking direction is one or more to three or less.

Yet another preferred embodiment of the present invention provides amethod for manufacturing a multilayer ceramic capacitor which includes amultilayer body provided with a plurality of stacked dielectric layersincluding a dielectric ceramic that includes a plurality of crystalgrains and a plurality of internal electrodes disposed at a plurality ofinterfaces between the dielectric layers, and the method preferablyincludes the steps of preparing a ceramic slurry by blending powderincluding a Ba and Ti containing perovskite compound, an La containingcompound powder, an Mg containing compound powder, an Mn containingcompound powder and an Al containing compound powder into a slurry inwhich a content of Ti is set to 100 molar parts, a fraction of eachcontent of La, Mg, Mn and Al relative to the content of Ti is in a rangethat La is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molarpart or less, Mn is about 1.0 to about 3.0 molar parts and Al is about0.5 to about 2.5 molar parts; obtaining a ceramic green sheet by formingthe ceramic slurry into a sheet; providing an unfired multilayer body bystacking the ceramic green sheet and a conductor pattern which definesand serves as the internal electrode after firing; and firing theunfired multilayer body to provide the multilayer body which isconfigured to have the internal electrode being disposed between thedielectric layers, and an average number of crystal grains included ineach of the dielectric layers in the stacking direction is one or moreto three or less.

Since multilayer ceramic capacitors according to various preferredembodiments of the present invention satisfy such conditions that themultilayer body, which is provided with a plurality of stackeddielectric layers (dielectric ceramic layers) including a dielectricceramic that includes a plurality of crystal grains and a plurality ofinternal electrodes disposed at a plurality of interfaces between thedielectric layers, includes a Ba and Ti containing perovskite compoundand La, Mg, Mn and Al, and in a case in which a content of Ti is set to100 molar parts, a fraction of each content of La, Mg, Mn and Alrelative to the content of Ti is such that La is about 0.2 to about 1.2molar parts, Mg is about 0.1 molar part or less, Mn is about 1.0 toabout 3.0 molar parts and Al is about 0.5 to about 2.5 molar parts, andan average number of crystal grains included in each of the dielectriclayers in the stacking direction is one or more to three or less, therelative dielectric constant of the dielectric layer is high, whichenables it to be made compact in size while having a large capacitance,and moreover, the Mean Time To Failure (“MTTF”) of the product at thehigh temperature load test is high, which makes it possible to obtain amultilayer ceramic capacitor with a high reliability.

Specifically, when the Ba and Ti containing perovskite compound is addedwith La, Mg, Mn and Al, if the fraction of each content of La, Mg, Mnand Al relative to the content of Ti is controlled to be within theranges of various preferred embodiments of the present invention and theaverage number of crystal grains included in each of the dielectriclayers in the stacking direction is reduced (the number of grainboundaries is reduced) to three or less, it is possible to furtherimprove the insulation deterioration tolerance while maintaining therelative dielectric constant high. In other words, in the multilayerceramic capacitors according to various preferred embodiments of thepresent invention, the grain boundary present in the dielectric layerdeteriorates in the insulation property, leading to failure, and thusreducing the number of grain boundaries will make it possible to improvethe characteristics.

In a case where the multilayer ceramic capacitors of various preferredembodiments of the present invention are configured to satisfy suchconditions that the multilayer body provided with a plurality of stackeddielectric layers and a plurality of internal electrodes disposed at aplurality of interfaces between the dielectric layers is subjected to adissolution treatment to form a solution, and if a content of Ti is setto 100 molar parts, a fraction of each content of La, Mg, Mn and Alrelative to the content of Ti in the solution is in a range that La isabout 0.2 to about 1.2 molar parts, Mg is about 0.1 molar part or less,Mn is about 1.0 to about 3.0 molar parts and Al is about 0.5 to about2.5 molar parts, and an average number of crystal grains included ineach of the dielectric layers in the stacking direction is one or moreto three or less, the relative dielectric constant of the dielectriclayer is high, which enables it to be made compact in size while havinga large capacitance, and moreover, the MTTF of the product at the hightemperature load test is high, which makes it possible to obtain amultilayer ceramic capacitor with a high reliability.

In a case where the multilayer ceramic capacitors of various preferredembodiments of the present invention are configured to satisfy suchconditions that the dielectric layer constituting the multilayer bodyincluding a Ba and Ti containing perovskite compound, La, Mg, Mn and Al,and in a case where a content of Ti is set to 100 molar parts, afraction of each content of La, Mg, Mn and Al relative to a content ofTi is in a range that La is about 0.2 to about 1.2 molar parts, Mg isabout 0.1 molar part or less, Mn is about 1.0 to about 3.0 molar partsand Al is about 0.5 to about 2.5 molar parts, and an average number ofcrystal grains included in each of the dielectric layers in the stackingdirection is one or more to three or less, the relative dielectricconstant of the dielectric layer is high, which enables it to be madecompact in size while having a large capacitance, and moreover, the MTTFof the product at the high temperature load test is high, which makes itpossible to obtain a multilayer ceramic capacitor with a highreliability.

Since a method for manufacturing the multilayer ceramic capacitoraccording to a preferred of the present invention is configured toprepare a ceramic slurry by blending powder including a Ba and Ticontaining perovskite compound, an La containing compound powder, an Mgcontaining compound powder, an Mn containing compound powder and an Alcontaining compound powder into a slurry in which a content of Ti is setto 100 molar parts, a fraction of each content of La, Mg, Mn and Alrelative to the content of Ti is in a range that La is about 0.2 toabout 1.2 molar parts, Mg is about 0.1 molar part or less, Mn is about1.0 to about 3.0 molar parts and Al is about 0.5 to about 2.5 molarparts, to obtain a ceramic green sheet by forming the ceramic slurryinto a sheet, to provide an unfired multilayer body by stacking theceramic green sheet and a conductor pattern which defines and serves asthe internal electrode after firing, to fire the unfired multilayer bodyto provide the multilayer body which is configured in such a manner thatthe internal electrode is disposed between the dielectric layers and anaverage number of crystal grains included in each of the dielectriclayers in the stacking direction is one or more to three or less, it ispossible to manufacture the multilayer ceramic capacitor satisfying theabove-mentioned conditions of the present invention efficiently.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a multilayer ceramic capacitor accordingto a preferred embodiment of the present invention.

FIG. 2 is a front cross-sectional view of a multilayer ceramic capacitoraccording to a preferred embodiment of the present invention.

FIG. 3 is a view for explaining a method of measuring an average numberof crystal grains in each dielectric layer of a multilayer ceramiccapacitor according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention aredescribed to explain the features of the present invention in detail.

First, a non-limiting example of a method of manufacturing a multilayerceramic capacitor according to a preferred embodiment of the presentinvention will be described.

To prepare a multilayer ceramic capacitor, firstly, as a startingmaterial for a Ba and Ti containing perovskite compound (barium titanatebased composite oxide), BaCO₃ powder and TiO₂ powder were prepared,respectively.

Then, each powder was weighed such that the fraction of the content ofBa relative to the content of Ti is 102.5 molar parts relative to 100molar parts of Ti.

The weighted powder was mixed by a ball mill with water serving as amedium, pre-fired at 1050° C., and pulverized to provide the Ba and Ticontaining perovskite compound powder (ceramic powder).

In the Ba and Ti containing a perovskite compound, Ca and Sr may beincluded into the site of Ba, and Zr and Hf may be included into thesite of Ti.

In the present preferred embodiment, although the pre-firing waspreferably performed at 1050° C., the pre-firing temperature is notlimited thereto, and it may be any appropriately selected temperaturesuitable for obtaining desired characteristics.

Thereafter, to the perovskite compound powder prepared as describedabove, R₂O₃ (R═La, Gd, Dy), Al₂O₃, MgCO₃ and MnCO₃ were added so thatthe fraction of content of each added component relative to the contentof Ti in the powder is equal to each corresponding fraction (molar part)listed in Table 1A and Table 1B relative to 100 molar parts of Ti, andSiO₂ was added at the fraction of 1.5 molar parts. The mixture wasblended in water by a ball mill to provide the dielectric material.

The obtained dielectric material was dissolved in acid and subjected toICP emission spectrometry, it was confirmed that the composition thereofis substantially identical to the composition listed in Table 1A andTable 1B.

The dielectric material was combined with a polyvinyl butyral-basedbinder and an organic solvent such as ethanol, and followed with wetblending by a ball mill to prepare a ceramic slurry.

Subsequently, the ceramic slurry was formed into a sheet by a doctorblade method in such a manner that the thickness of the dielectric layer(dielectric ceramic layer) after firing is 2.0 μm, and thus, arectangular or substantially rectangular ceramic green sheet wasobtained. Next, a conductive paste containing Ni as a conductivecomponent was printed on the ceramic green sheet through screen printingto provide a conductor pattern (internal electrode pattern) whichdefines and serves as an internal electrode after firing.

A plurality of the ceramic green sheets each provided with a conductorpattern (internal electrode pattern) were stacked in such a manner thatthe end surfaces where the conductor pattern is exposed are opposite toeach other alternately to provide an unfired multilayer body.Thereafter, the unfired multilayer body was heated to 270° C. under anair atmosphere to remove the binder.

Thereafter, the unfired multilayer body after removal of the binder wasfired by keeping it at 1160° C. to 1260° C. for 2 hours under a reducingatmosphere composed of H₂—N₂—H₂O gas to provide a fired multilayer body.In the firing step, the temperature where the unfired multilayer bodywas kept for 2 hours was appropriately adjusted in the abovementionedrange of 1160° C. to 1260° C., and thus, the average number of crystalgrains (average grain number) contained in each dielectric layer(dielectric ceramic layer) in the stacking direction was controlled.

Next, a Cu electrode paste was applied to the end surfaces of the firedmultilayer body obtained as described above and baked to provideexternal electrodes, and thus, the multilayer ceramic capacitor (sampleswith sample numbers of 1 to 30 in Table 1A and Table 1B forcharacteristic measurement) was obtained. A perspective view of themultilayer ceramic capacitor is schematically illustrated in FIG. 1 anda front cross-sectional view thereof is schematically illustrated inFIG. 2.

As illustrated in FIGS. 1 and 2, the multilayer ceramic capacitor isconfigured to include a multilayer body (multilayer ceramic element) 10provided with a plurality of stacked dielectric layers (dielectricceramic layers) 11 and a plurality of internal electrodes 12 disposed ata plurality of interfaces between dielectric layers 11, and a pair ofexternal electrodes (Cu electrodes) 13 a and 13 b disposed on both endsurfaces of multilayer body 10 in conduction with internal electrodes 12exposed alternately on opposite end surfaces.

Regarding the dimensions of the multilayer ceramic capacitors preparedas described above, the width (W) thereof preferably was about 1.0 mm,the length (L) thereof preferably was about 2.0 mm, and the thickness(T) thereof preferably was about 0.4 mm, for example. The thickness ofone dielectric layer interposed between the internal electrodespreferably was about 2.0 μm, and the thickness of one internal electrode12 preferably was about 1.0 μm, for example. The total number ofeffective dielectric ceramic layers excluding the outer layerspreferably is 100, and the opposite area of electrodes per layerpreferably was 1.6 mm², for example.

After the external electrodes (Cu electrodes) were removed from themultilayer ceramic capacitor obtained as mentioned above, the multilayerceramic capacitor without the external electrodes was dissolved in acidand subjected to ICP emission spectrometry, it was confirmed that themultilayer ceramic capacitor, excluding the ingredient Ni constitutingthe internal electrode, had a composition substantially identical toeach composition listed in Table 1A and Table 1B.

The average number of crystal grains (average grain number) contained ineach dielectric layer was determined by an interception method.Specifically, the average number of crystal grains in each dielectriclayer was measured as follows.

First, the multilayer body (multilayer ceramic device) 10 was sectionedapproximately at the midpoint of the length (L) direction of themultilayer ceramic capacitor along the thickness (T) direction and thewidth (W) direction. Then, in order to make clear the boundary (grainboundary) between the grains in dielectric layer 11, the sectionedmultilayer body (sample) was subjected to heat treatment. Thetemperature of the heat treatment is set to such a temperature that atwhich the grain growth will not occur and the grain boundary will becomeclear, and in the present preferred embodiment, it was set to 1000° C.,for example.

After multilayer body 10 was sectioned, a region (substantially thecentral region in the section surface) in the section surface (WT face)around a position having roughly ½W in the W direction and ½T in the Tdirection was determined as a measurement region F (see FIG. 3), and themeasurement region was observed with a scanning electron microscope(SEM) at a magnification power of 10,000 times.

First, 200 crystal grains were randomly extracted from the measurementregion. The grain size of each of 200 crystal grains was measuredaccording to the diameter method in which the maximum length of eachcrystal grain in a direction parallel to the principal surface of theinner electrode is regarded as the grain size, and an average value ofthe grain sizes was calculated as the average grain size.

Then, 5 dielectric layers were randomly extracted from the SEM image ofthe measurement region. In each layer, 20 lines (a total of 100 lines in5 layers), each of which is perpendicular to the principal surface ofthe inner electrode adjacent to each layer, were drawn at an intervalequal to the average grain size, and the number of crystal grainssectioning each line were counted. The number of crystal grains weresummed up and the sum was divided by the total number 100 of the linesto give a value A. The same was performed for 5 samples having the samesample number, and the average value of the obtained A was used as theaverage number of crystal grains per element (the average number ofcrystal grains per dielectric layer in the stacking direction).

The measurement results of the average number of crystal grains (averagegrain number) per dielectric layer for the samples (multilayer ceramiccapacitor) No. 1 to 30 prepared according to the present preferredembodiment are listed together in Table 1A and Table 1B.

For the multilayer ceramic capacitor prepared as described above, thehigh temperature load test was performed. In the high temperature loadtest, the multiplayer ceramic capacitor was applied with a voltage of 30V at a temperature of 150° C., and the aging variations on insulationresistance were observed.

The high temperature load test was performed for 100 samples having thesame sample number, and if the insulation resistance drops to 100 kQ orless, it is determined that the sample has failed, and the MTTF at 50%was determined by the Weibull analysis of the failure time. Any samplehaving the MTTF of 650 h or less was determined as a non-standardproduct.

The results of the MTTF in the high temperature load test for thesamples (multilayer ceramic capacitor) No. 1 to 30 prepared according tothe present preferred embodiment are listed together in Table 1A andTable 1B

The relative dielectric constant of the dielectric layer was calculatedfrom the capacitance of the multilayer ceramic capacitor. Thecapacitance of the multilayer ceramic capacitor was measured by using adigital LCR meter (HP 4284A HP by Hewlett-Packard Development Company)at a frequency of 1 kHz and a measuring voltage of 1 Vrms/μm. In thepresent preferred embodiment, the standard level of the relativedielectric constant ∈_(r) was set to 3000 or more.

The relative dielectric constant ∈_(r) of the dielectric layer in eachof the samples No. 1 to 30 prepared in the present preferred embodimentis listed in Table 1A and Table 1B.

TABLE 1A Dielectric High Constant Composition Temperature ε_(r) (molarparts/100 molar Average Load Test (1 kHz, Sample parts of Ti) Gain MTTF1 Vrms/ No. La Gd Dy Mg Mn Al Number (h) μm)  *1 0.1 — — — 1.5 0.5 6.840 2200  *2 0.1 — — — 1.5 0.5 1.8 110 3400  *3 0.2 — — — 1.5 0.5 7.5 4802100   4 0.2 — — — 1.5 0.5 1.7 970 3300  *5 0.5 — — — 1.5 1.5 6.9 5102300  6 0.5 — — — 1.5 1.5 2.8 910 3000  7 0.5 — — — 1.5 1.5 2.1 11803200  *8 0.5 — — 0.15 2.0 1.5 7.2 160 2100  *9 0.5 — — 0.15 2.0 1.5 2.0140 3100 *10 0.7 — — 0.10 2.0 1.5 6.6 440 2000  11 0.7 — — 0.10 2.0 1.52.2 840 3100 *12 1.2 — — — 3.0 2.5 7.1 560 2400  13 1.2 — — — 3.0 2.51.9 1610 3200 *14 1.5 — — — 2.5 1.5 2.2 110 5600 *15 0.5 — — — 3.0 0.21.8 170 3600

TABLE 1B Dielectric High Constant Composition Temperature ε_(r) (molarparts/100 molar Average Load Test (1 kHz, Sample parts of Ti) Gain MTTF1 Vrms/ No. La Gd Dy Mg Mn Al Number (h) μm) *16 0.5 — — — 3.0 3.0 3.0500 2900  17 0.5 — — — 3.0 0.5 3.0 850 3200  18 0.5 — — — 3.0 0.5 2.2960 3400  19 0.5 — — — 2.0 1.0 2.0 1010 3300 *20 0.5 — — — 3.0 0.5 7.5150 2300 *21 0.5 — — — 3.0 2.5 7.2 210 2100  22 1.0 — — 0.05 1.0 1.5 2.1900 3200 *23 1.0 — — 0.05 0.7 1.5 2.5 370 3300 *24 1.0 — — — 3.5 2.0 2.9550 2700 *25 1.0 — — 0.05 1.0 1.5 8.1 250 2000 *26 1.0 — — 0.05 3.0 1.56.8 300 2200 *27 — 0.5 — 0.05 1.5 1.5 2.2 50 5200 *28 — 0.5 — 0.05 1.51.5 9.5 490 2500 *29 — — 0.5 0.05 1.5 1.5 2.5 20 4000 *30 — — 0.5 0.051.5 1.5 10.4 360 2300

The samples with an asterisk mark (*) appearing before the sample numberin Table 1A and Table 1B are samples that failed to satisfy theconditions of the present invention, and the other samples are thosesatisfying the conditions of the present invention.

It was confirmed from Table 1A and Table 1B that the samples satisfyingthe conditions of the present invention (without an asterisk markattached afore the sample number) have an MTTF value of 650 h or more inthe high temperature load test, and thus, have a great insulationdeterioration tolerance and a high reliability.

Moreover, it was confirmed that each dielectric layer in the samplessatisfying the conditions of the present invention (without an asteriskmark appearing before the sample number) has a higher relativedielectric constant.

On the contrary, for those samples such as samples No. 1 and 2 addedwith a small amount of La at 0.1 molar parts, it was confirmed that theinsulation deterioration tolerance deteriorates remarkably in the hightemperature load test regardless of the average number of crystal grains(average grain number) per dielectric layer. In addition, for the samplesuch as sample No. 14 added with an amount of La at 1.5 molar partsexceeding the range of the present invention, it was confirmed that theinsulation deterioration tolerance deteriorates remarkably in the hightemperature load test.

Further, for those samples having a greater average number of crystalgrains (greater than three) per dielectric layer such as samples No. 3,5, 10, 12, 20, 21, 25 and 26, even though the content of La is in therange of the present invention, compared to the samples having theaverage number of crystal grains per dielectric layer within the rangeof the present invention, it was confirmed that the tolerancedeteriorates in the high temperature load test.

In addition, for the samples such as samples No. 8 and 9 added with anamount of Mg exceeding the range of the present invention, compared tothe samples added with an amount of Mg within the range of the presentinvention, it was confirmed that the tolerance deteriorates in the hightemperature load test regardless of the average number of crystal grainsper dielectric layer.

Further, for the samples such as samples No. 15 and 16 added with anamount of Al out of the range of the present invention, compared to thesamples added with an amount of Al within the range of the presentinvention, it was confirmed that the tolerance deteriorates in the hightemperature load test.

Further, for the samples such as samples No. 23 and 24 added with anamount of Mn out of the range of the present invention, compared to thesamples added with an amount of Mn within the range of the presentinvention, it was confirmed that the tolerance deteriorates in the hightemperature load test.

Furthermore, for those samples such as samples No. 27 to 30 containingthe rare earth elements Gd and Dy rather than La and thereby notsatisfying the conditions of the present invention, compared to thesamples within the scope of the present invention, it was confirmed thatthe tolerance deteriorates in the high temperature load test.

From the results mentioned above, it was confirmed that the multilayerceramic capacitor which includes a dielectric layer having a highrelative dielectric constant, and has a great insulation deteriorationtolerance in the high temperature load test and a high reliability isobtained from those samples in which the fraction of each content of La,Mg, Mn and Al relative to the content of Ti determined by the ICPemission spectrometry performed on the multilayer body is in the rangethat La is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molarpart or less, Mn is about 1.0 to about 3.0 molar parts and Al is about0.5 to about 2.5 molar parts, assuming that the content of Ti is 100molar parts, and the average number of crystal grains in each dielectriclayer is one or more to three or less.

In the above preferred embodiments, the fraction of each content of La,Mg, Mn and Al relative to the content of Ti preferably has beendetermined for the multilayer body, and it is also acceptable todetermine the fraction of each content of La, Mg, Mn and Al relative tothe content of Ti for the dielectric layer constituting the multilayerbody.

The present invention is not intended to be limited to the abovepreferred embodiments, the number of dielectric layers constituting themultilayer body, the number of internal electrodes and/or the fractionof the content of La, Mg, Mn and Al relative to the content of Ti in themultilayer body or in the dielectric body may be applied or modified invarious ways within the scope of the present invention.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A multilayer ceramic capacitor comprising: amultilayer body including a plurality of stacked dielectric layersincluding a dielectric ceramic that includes a plurality of crystalgrains and a plurality of internal electrodes disposed at a plurality ofinterfaces between the dielectric layers; and an external electrodeprovided on an outer surface of the multilayer body and electricallyconnected to some of the plurality of inner electrode; wherein themultilayer body includes a Ba and Ti containing perovskite compound, andLa, Mg, Mn and Al; in a case in which a content of Ti is set to 100molar parts, a fraction of each content of La, Mg, Mn and Al relative tothe content of Ti is such that La is about 0.2 to about 1.2 molar parts,Mg is about 0.1 molar part or less, Mn is about 1.0 to about 3.0 molarparts and Al is about 0.5 to about 2.5 molar parts; and an averagenumber of the crystal grains included in each of the plurality ofdielectric layers in a stacking direction is one or more to three orless.
 2. The multilayer ceramic capacitor according to claim 1, whereinthe multilayer body includes a width of about 1.0 mm, a length of about2.0 mm, and a thickness of about 0.4 mm, and a thickness of each of theplurality of dielectric layer is about 2.0 μm, and a thickness of eachof the plurality of internal electrodes is about 1.0 μm.
 3. A multilayerceramic capacitor comprising: a multilayer body including a plurality ofstacked dielectric layers including a dielectric ceramic that includes aplurality of crystal grains and a plurality of internal electrodesdisposed at a plurality of interfaces between the dielectric layers; andan external electrode provided on an outer surface of the multilayerbody and electrically connected to some of the plurality of innerelectrode; wherein the multilayer body includes a Ba and Ti containingperovskite compound, and La, Mg, Mn and Al; in a case in which themultilayer body is subjected to a dissolution treatment to form asolution and a content of Ti is set to 100 molar parts, a fraction ofeach content of La, Mg, Mn and Al relative to the content of Ti is suchthat La is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molarpart or less, Mn is about 1.0 to about 3.0 molar parts and Al is about0.5 to about 2.5 molar parts; and an average number of the crystalgrains included in each of the plurality of dielectric layers in astacking direction is one or more to three or less.
 4. The multilayerceramic capacitor according to claim 3, wherein the multilayer bodyincludes a width of about 1.0 mm, a length of about 2.0 mm, and athickness of about 0.4 mm, and a thickness of each of the plurality ofdielectric layer is about 2.0 μm, and a thickness of each of theplurality of internal electrodes is about 1.0 μm.
 5. A multilayerceramic capacitor comprising: a multilayer body including a plurality ofstacked dielectric layers including a dielectric ceramic that includes aplurality of crystal grains and a plurality of internal electrodesdisposed at a plurality of interfaces between the dielectric layers; andan external electrode provided on an outer surface of the multilayerbody and electrically connected to some of the plurality of innerelectrode; wherein the plurality of dielectric layers include a Ba andTi containing perovskite compound, and La, Mg, Mn and Al; in a case inwhich a content of Ti is set to 100 molar parts, a fraction of eachcontent of La, Mg, Mn and Al relative to the content of Ti is such thatLa is about 0.2 to about 1.2 molar parts, Mg is about 0.1 molar part orless, Mn is about 1.0 to about 3.0 molar parts and Al is about 0.5 toabout 2.5 molar parts; and an average number of the crystal grainsincluded in each of the dielectric layers in a stacking direction is oneor more to three or less an average number of the crystal grainsincluded in each of the plurality of dielectric layers in the stackingdirection being one or more to three or less.
 6. The multilayer ceramiccapacitor according to claim 5, wherein the multilayer body includes awidth of about 1.0 mm, a length of about 2.0 mm, and a thickness ofabout 0.4 mm, and a thickness of each of the plurality of dielectriclayer is about 2.0 μm, and a thickness of each of the plurality ofinternal electrodes is about 1.0 μm.
 7. A method for manufacturing amultilayer ceramic capacitor which includes a multilayer body providedwith a plurality of stacked dielectric layers including a dielectricceramic that includes a plurality of crystal grains and a plurality ofinternal electrodes disposed at a plurality of interfaces between thedielectric layers, the method comprising the steps of: preparing aceramic slurry by blending powder including a Ba and Ti containingperovskite compound, an La containing compound powder, an Mg containingcompound powder, an Mn containing compound powder and an Al containingcompound powder into a slurry in which a content of Ti is set to 100molar parts, a fraction of each content of La, Mg, Mn and Al relative tothe content of Ti is such that La is about 0.2 to about 1.2 molar parts,Mg is about 0.1 molar part or less, Mn is about 1.0 to about 3.0 molarparts and Al is about 0.5 to about 2.5 molar parts; obtaining a ceramicgreen sheet by forming the ceramic slurry into a sheet; providing anunfired multilayer body by stacking the ceramic green sheet and aconductor pattern which defines the plurality of internal electrodesafter firing; and firing the unfired multilayer body to provide themultilayer body which is configured in such a manner that each of theplurality of internal electrodes are disposed between adjacent pairs ofthe plurality of dielectric layers, and an average number of the crystalgrains included in each of the dielectric layers in a stacking directionis one or more to three or less.
 8. The method according to claim 7,wherein each powder was weighed such that the fraction of the content ofBa relative to the content of Ti is 102.5 molar parts relative to 100molar parts of Ti.
 9. The method according to claim 7, wherein theblending was performed by mixing in a ball mill while using water as amedium, pre-firing and pulverizing to provide a ceramic powder.
 10. Themethod according to claim 7, wherein in the Ba and Ti containingperovskite compound, Ca and Sr are included in a site of Ba, and Zr andHf are included in a site of Ti.
 11. The method according to claim 7,wherein the step of preparing the ceramic slurry includes adding R₂O₃(R═La, Gd, Dy), Al₂O₃, MgCO₃ and MnCO₃ to the perovskite compoundpowder.
 12. The method according to claim 7, wherein the step ofpreparing the ceramic slurry includes adding a polyvinyl butyral-basedbinder and an organic solvent, and wet blending by a ball mill toprepare the ceramic slurry.
 13. The method according to claim 7, whereinthe step of forming the ceramic slurry into the sheet by a doctor blademethod.
 14. The method according to claim 7, wherein a thickness of thesheet is about 2.0 μm.
 15. The method according to claim 7, wherein thestep of firing is performed at temperature of about 1160° C. to about1260° C.
 16. The method according to claim 7, further comprising formingexternal electrodes on end surfaces of the fired multilayer body. 17.The method according to claim 7, wherein the fired multilayer bodyincludes a width of about 1.0 mm, a length of about 2.0 mm, and athickness of about 0.4 mm, and a thickness of each of the plurality ofdielectric layer is about 2.0 μm, and a thickness of each of theplurality of internal electrodes is about 1.0 μm.